An FAQ reply by John Rundle at praticalfishkeeping.co.uk. A straight forward answer to why betta breeding sometimes just doesnt go your way! It's nature. It's life. You can't always predict things. And not everyting goes 100% every time. Keep that in mind and be patient =)
Why won’t my Siamese fighters, Betta splendens, breed?When all factors are correct, the popular Siamese fighter is not difficult to breed - but when something is not quite right, these fish can frustrate even the most experienced fishkeeper. To put it bluntly, the Siamese fighter can be unpredictable.A breeding project can break down because the males may worry and kill the female, or the male will not blow a bubblenest and the pair will not breed. And if the male is keen but the female is not in breeding condition, you are more likely to have a female with no fins, or even dead.